While not limited thereto, the present invention is particularly adapted for use with fast breeder nuclear reactors employing a liquid sodium as a heat transfer agent. In such reactors, a fuel rod cladding alloy must be used which has good resistance to corrosion by the sodium on the outer surface of the cladding (i.e., wall thinning). At the same time, the cladding material should act as a diffusion barrier to outward diffusion of .sup.54 Mn from the fuel cladding to the sodium.
At the present time, nickel-chromium base alloys or stainless steel containing at least 10% nickel are used as the cladding material. While these materials are generally satisfactory for their intended usage, there is always a need for further improvement in corrosion resistance and other properties in the highly-corrosive liquid sodium environment.